When a compound having a carboxyl group is dissolved in a solvent phase containing water for reaction, it has acidic conditions of various intensities due to dissociation of hydrogen atoms. In particular, in the case of molecules containing two or more carboxylic acid functional groups such as dicarboxylic acid, the acidity of the solution may be higher depending on the type of molecule. As the temperature is raised for the reaction, the intensity of the acid will form a very strongly acidic conditions of pH=1 or less.
In particular, for the hydrogenation of aromatic ring compounds, a high temperature of 150 to 300° C. is essentially required. It is obvious that the pH of the acidic aqueous solution decreases in proportion to the temperature. Therefore, for the aromatic ring hydrogenation of isophthalic acid, which is an aromatic compound, it is necessary to use a catalyst having acid resistance not only at high temperature but also strongly acidic condition (pH=1 or less), thereby producing 1,3-cyclohexane dicarboxylic acid which is industrially economical.
Conventionally, there are many catalyst systems using palladium, but there were no cases applied to the aromatic ring hydrogenation of isophthalic acid. Even if it was used for the hydrogenation reaction of other organic compounds, any method for maintaining medium- to long-term activity under high temperature-strong acid conditions has not been suggested.
Therefore, there is a need to develop a new manufacturing process technology that can replace the conventionally known process for producing 1,3-cyclohexanedicarboxylic acid.